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Equity Investments - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($) MW
Wind Turbine Generators | Tenaska | Tenaska PPA | Minnesota Power
Investments In ATC [Roll Forward]
Generating capacity counterparty owned (MegaWatt) | MW	250
Long-term contract for purchase of electric power	20 years
ATC
Investments In ATC [Roll Forward]
Ownership percentage	8.00%
Authorized return on equity	10.02%
Authorized return on equity, including incentive adder	10.52%
Basis point incentive adder	0.50%
Approximate annual reduction in pretax income for FERC proposal to limit incentive adder, Allete's proportionate share | $	$ 1
Nobles 2
Investments In ATC [Roll Forward]
Ownership percentage	49.00%

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Approximate Annual Reduction In Pretax Income For FERC Proposal To Limit Incentive Adder, ALLETE's Proportionate Share

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- Definition

Basis Point Incentive Adder

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The approved percentage return on common equity, including an incentive adder for participation in a regional transmission organization dedicated to the utility plant in the investee accounted for under the equity method of accounting.

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Generating Capacity Counterparty Owned (MW)

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Investments In ATC

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Term in years of long-term contract to purchase electricity from a production plant constructed and financed by a public utility district, cooperative, or other organization.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481687/323-10-50-3

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Percentage of public utility's approved return on equity.

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